Mapping Experiences

CHAPTER 13

CHAPTER 13. Spatial Maps and Ecosystem Models

IN THIS CHAPTER

• Introduction to spatial maps
• Isometric projections and ecosystem models
• Case Study: Gigamapping: Canadian Governance in the Digital Era

The cause of the great cholera outbreak in London in 1854 was initially unclear. Prior to Louis Pasteur’s germ theory, many thought the disease was in the air. John Snow, a London physician, had a different explanation. He believed cholera was in the water. After microscopic examinations were inconclusive, Snow instead analyzed the spread of cholera to prove his hunch.

To do this, Snow mapped cholera cases in Soho, London (Figure 13-1). The resulting patterns demonstrated causality: proximity to a certain water pump correlated to cholera cases with high predictability. The decline of cholera is credited to Snow’s recommendation to shut down that pump.

FIGURE 13-1. John Snow’s map of London during the great cholera outbreak of 1854. The red circle highlights the water pump that was the source of the disease.

Snow’s map contains multiple layers of information—streets, houses with cholera cases, and water pumps—just enough to reveal previously undetected evidence (in this case, the cause of a disease). The approach is simple but effective: Snow was able to generate a hypothesis based on his simple map: if the city shuts down a specific pump, then cases ...